<?php

/*
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Curl based implementation of apiIO.
 *
 * @author Chris Chabot <chabotc@google.com>
 * @author Chirag Shah <chirags@google.com>
 */
require_once 'Google_CacheParser.php';

class Google_CurlIO implements Google_IO {

    const CONNECTION_ESTABLISHED = "HTTP/1.0 200 Connection established\r\n\r\n";
    const FORM_URLENCODED = 'application/x-www-form-urlencoded';

    private static $ENTITY_HTTP_METHODS = array("POST" => null, "PUT" => null);
    private static $HOP_BY_HOP = array(
        'connection', 'keep-alive', 'proxy-authenticate', 'proxy-authorization',
        'te', 'trailers', 'transfer-encoding', 'upgrade');
    private $curlParams = array(
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_FOLLOWLOCATION => 0,
        CURLOPT_FAILONERROR => false,
        CURLOPT_SSL_VERIFYPEER => true,
        CURLOPT_HEADER => true,
        CURLOPT_VERBOSE => false,
    );

    /**
     * Perform an authenticated / signed apiHttpRequest.
     * This function takes the apiHttpRequest, calls apiAuth->sign on it
     * (which can modify the request in what ever way fits the auth mechanism)
     * and then calls apiCurlIO::makeRequest on the signed request
     *
     * @param Google_HttpRequest $request
     * @return Google_HttpRequest The resulting HTTP response including the
     * responseHttpCode, responseHeaders and responseBody.
     */
    public function authenticatedRequest(Google_HttpRequest $request) {
        $request = Google_Client::$auth->sign($request);
        return $this->makeRequest($request);
    }

    /**
     * Execute a apiHttpRequest
     *
     * @param Google_HttpRequest $request the http request to be executed
     * @return Google_HttpRequest http request with the response http code, response
     * headers and response body filled in
     * @throws Google_IOException on curl or IO error
     */
    public function makeRequest(Google_HttpRequest $request) {
        // First, check to see if we have a valid cached version.
        $cached = $this->getCachedRequest($request);
        if ($cached !== false) {
            if (Google_CacheParser::mustRevalidate($cached)) {
                $addHeaders = array();
                if ($cached->getResponseHeader('etag')) {
                    // [13.3.4] If an entity tag has been provided by the origin server,
                    // we must use that entity tag in any cache-conditional request.
                    $addHeaders['If-None-Match'] = $cached->getResponseHeader('etag');
                } elseif ($cached->getResponseHeader('date')) {
                    $addHeaders['If-Modified-Since'] = $cached->getResponseHeader('date');
                }

                $request->setRequestHeaders($addHeaders);
            } else {
                // No need to revalidate the request, return it directly
                return $cached;
            }
        }

        if (array_key_exists($request->getRequestMethod(), self::$ENTITY_HTTP_METHODS)) {
            $request = $this->processEntityRequest($request);
        }

        $ch = curl_init();
        curl_setopt_array($ch, $this->curlParams);
        curl_setopt($ch, CURLOPT_URL, $request->getUrl());
        if ($request->getPostBody()) {
            curl_setopt($ch, CURLOPT_POSTFIELDS, $request->getPostBody());
        }

        $requestHeaders = $request->getRequestHeaders();
        if ($requestHeaders && is_array($requestHeaders)) {
            $parsed = array();
            foreach ($requestHeaders as $k => $v) {
                $parsed[] = "$k: $v";
            }
            curl_setopt($ch, CURLOPT_HTTPHEADER, $parsed);
        }

        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $request->getRequestMethod());
        curl_setopt($ch, CURLOPT_USERAGENT, $request->getUserAgent());
        $respData = curl_exec($ch);

        // Retry if certificates are missing.
        if (curl_errno($ch) == CURLE_SSL_CACERT) {
            error_log('SSL certificate problem, verify that the CA cert is OK.'
                    . ' Retrying with the CA cert bundle from google-api-php-client.');
            curl_setopt($ch, CURLOPT_CAINFO, dirname(__FILE__) . '/cacerts.pem');
            $respData = curl_exec($ch);
        }

        $respHeaderSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
        $respHttpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $curlErrorNum = curl_errno($ch);
        $curlError = curl_error($ch);
        curl_close($ch);
        if ($curlErrorNum != CURLE_OK) {
            //throw new Google_IOException("HTTP Error: ($respHttpCode) $curlError");
        }

        // Parse out the raw response into usable bits
        list($responseHeaders, $responseBody) =
                self::parseHttpResponse($respData, $respHeaderSize);

        if ($respHttpCode == 304 && $cached) {
            // If the server responded NOT_MODIFIED, return the cached request.
            if (isset($responseHeaders['connection'])) {
                $hopByHop = array_merge(
                        self::$HOP_BY_HOP, explode(',', $responseHeaders['connection'])
                );

                $endToEnd = array();
                foreach ($hopByHop as $key) {
                    if (isset($responseHeaders[$key])) {
                        $endToEnd[$key] = $responseHeaders[$key];
                    }
                }
                $cached->setResponseHeaders($endToEnd);
            }
            return $cached;
        }

        // Fill in the apiHttpRequest with the response values
        $request->setResponseHttpCode($respHttpCode);
        $request->setResponseHeaders($responseHeaders);
        $request->setResponseBody($responseBody);
        // Store the request in cache (the function checks to see if the request
        // can actually be cached)
        $this->setCachedRequest($request);
        // And finally return it
        return $request;
    }

    /**
     * @visible for testing.
     * Cache the response to an HTTP request if it is cacheable.
     * @param Google_HttpRequest $request
     * @return bool Returns true if the insertion was successful.
     * Otherwise, return false.
     */
    public function setCachedRequest(Google_HttpRequest $request) {
        // Determine if the request is cacheable.
        if (Google_CacheParser::isResponseCacheable($request)) {
            Google_Client::$cache->set($request->getCacheKey(), $request);
            return true;
        }

        return false;
    }

    /**
     * @visible for testing.
     * @param Google_HttpRequest $request
     * @return Google_HttpRequest|bool Returns the cached object or
     * false if the operation was unsuccessful.
     */
    public function getCachedRequest(Google_HttpRequest $request) {
        if (false == Google_CacheParser::isRequestCacheable($request)) {
            false;
        }

        return Google_Client::$cache->get($request->getCacheKey());
    }

    /**
     * @param $respData
     * @param $headerSize
     * @return array
     */
    public static function parseHttpResponse($respData, $headerSize) {
        if (stripos($respData, self::CONNECTION_ESTABLISHED) !== false) {
            $respData = str_ireplace(self::CONNECTION_ESTABLISHED, '', $respData);
        }

        if ($headerSize) {
            $responseBody = substr($respData, $headerSize);
            $responseHeaders = substr($respData, 0, $headerSize);
        } else {
            list($responseHeaders, $responseBody) = explode("\r\n\r\n", $respData, 2);
        }

        $responseHeaders = self::parseResponseHeaders($responseHeaders);
        return array($responseHeaders, $responseBody);
    }

    public static function parseResponseHeaders($rawHeaders) {
        $responseHeaders = array();

        $responseHeaderLines = explode("\r\n", $rawHeaders);
        foreach ($responseHeaderLines as $headerLine) {
            if ($headerLine && strpos($headerLine, ':') !== false) {
                list($header, $value) = explode(': ', $headerLine, 2);
                $header = strtolower($header);
                if (isset($responseHeaders[$header])) {
                    $responseHeaders[$header] .= "\n" . $value;
                } else {
                    $responseHeaders[$header] = $value;
                }
            }
        }
        return $responseHeaders;
    }

    /**
     * @visible for testing
     * Process an http request that contains an enclosed entity.
     * @param Google_HttpRequest $request
     * @return Google_HttpRequest Processed request with the enclosed entity.
     */
    public function processEntityRequest(Google_HttpRequest $request) {
        $postBody = $request->getPostBody();
        $contentType = $request->getRequestHeader("content-type");

        // Set the default content-type as application/x-www-form-urlencoded.
        if (false == $contentType) {
            $contentType = self::FORM_URLENCODED;
            $request->setRequestHeaders(array('content-type' => $contentType));
        }

        // Force the payload to match the content-type asserted in the header.
        if ($contentType == self::FORM_URLENCODED && is_array($postBody)) {
            $postBody = http_build_query($postBody, '', '&');
            $request->setPostBody($postBody);
        }

        // Make sure the content-length header is set.
        if (!$postBody || is_string($postBody)) {
            $postsLength = strlen($postBody);
            $request->setRequestHeaders(array('content-length' => $postsLength));
        }

        return $request;
    }

    /**
     * Set options that update cURL's default behavior.
     * The list of accepted options are:
     * {@link http://php.net/manual/en/function.curl-setopt.php]
     *
     * @param array $optCurlParams Multiple options used by a cURL session.
     */
    public function setOptions($optCurlParams) {
        foreach ($optCurlParams as $key => $val) {
            $this->curlParams[$key] = $val;
        }
    }

}